KR102556073B1 - Method and mask for producing watermarked paper, method for producing obtained watermarked paper mask, and method for authenticating watermarked paper - Google Patents

Abstract

A method of manufacturing security paper comprising the step of creating a watermark using a mask (10) attached to a wire of a paper machine, the mask having a bright area on the watermark. It comprises a network of elements (18) for forming light zones, said elements being connected by linking elements (15), said light zones being pixels of a raster image. Arranged like fields, the connecting elements form a raster image in which at least some of the elements 18 for forming bright zones appear as isolated pixels to the naked eye in transmitted light. sufficiently fine to result in the formation of pixels of

Description

Method and mask for producing watermarked paper, method for producing obtained watermarked paper mask, and method for authenticating watermarked paper

The present invention relates to a method for manufacturing watermarked security papers and papers and documents obtained thereby.

Watermarks have been used for a very long time in the field of security documents, by acting on and/or dewatering a fiber-deposition process, by changing the thickness of a paper substrate during manufacture. is formed

There have been many improvements to the creation of watermarks.

The present invention more particularly relates to a watermark that reproduces a halftone image.

Applicant's patents EP1122360 B1 and EP1252389 B1 describe methods for producing such watermarks, which are sold by the applicant under the trade name Pixel Watermark. A mask used in the manufacture of such a watermark can be conveniently obtained by machining or chemical etching of a metal plate. This process makes fabrication of high precision masks difficult, since the spatial resolution of details is, as a rule of thumb, at least 0.8 times the thickness. Thus, for a 0.5 mm thick mask, the apertures producible therein must have a size of at least 0.4 mm.

Other publications, namely WO2010/036104 A1, WO2011/117828 A1 or WO2011/081561 A1 also relate to the production of watermarks of this type.

Patent application WO2013/140126 A1 discloses a watermark-forming mask formed of a grid to which elements intended to form a pattern of watermarks are attached. The zones formed by the elements in the watermark appear to be separated from each other, which is presented as an advantage when reproducing Arabic characters. This document is not concerned with the problem of reproducing raster images.

There is a need to further improve watermarks that at least partially reproduce raster images, and corresponding manufacturing methods, in particular to increase the security provided by such watermarks.

The present invention achieves this object by a method for manufacturing security paper, said method comprising:

creating a watermark using a mask fixed to a wire of a paper machine, the mask comprising elements (18) for forming light zones in the watermark; , wherein the elements are connected by linking elements, the bright areas are arranged as pixels of a raster image, the connecting elements comprising the elements for forming bright areas. At least some of them are sufficiently thin to lead to the formation of pixels of a raster image that appear to the naked eye as isolated pixels in transmitted light.

The expressions “with the naked eye” or “by the naked eye” refer to observation by the human eye with normal vision from a distance of 25 cm under daylight without equipment.

The present invention allows visually attractive watermarks to be created, and since watermarks are difficult to imitate due to their high clarity, security against counterfeiting can be increased.

Another advantage is that it allows good dewatering of the paper during its formation.

In the prior art, bridges or even frames are placed on a forming wire with relative positions corresponding to the pattern to be reproduced and hold together various elements welded thereto, and when the watermark is observed with the naked eye, it is visibly visible. On the other hand, in the present invention, at least some elements of the watermark design appear to be separated from each other with the naked eye, which will allow new visual effects notable by people on the street to be obtained and expand the range of patterns that can be created. make it possible

The visual impression of softness created by the components of the pattern can be used to enhance the aesthetic appearance in particular. The watermark can be more easily recognized by people on the street. Thus, it no longer takes the form of rasters of lines at least partially connected together or rasters of lines connected together, as is the case with current pixel-type watermarks, but instead of dots whose connection points are no longer visible or barely visible. It is possible to obtain a new type of watermark having the form of a cloud or a cloud of lines.

Another subject of the invention is a watermark-forming mask for implementing the method according to the invention, comprising a set of elements for forming light zones, said Elements are connected by linking elements and arranged as pixels of a raster image, analogous to lines called "intaglio" lines in the field of banknotes, for example. Arranged in the form of like lines, the connecting elements are thin enough to be visually invisible in the watermark, and the elements to form bright areas are visible to the naked eye in transmitted light as isolated pixels in the image. This leads to the formation of pixels of a raster image that appear as isolated pixels.

raster image

A “raster image” is to be understood as an image formed by pixels arranged in a raster with variable spacing and/or size to create a halftone image. Multiple “grayscale levels” may be reproduced according to the density, size, height and/or amplitude of the pixels, or even the local opacity of the paper within each pixel. In this case, the grayscale levels preferably create a three-dimensional effect, for example a relief effect.

Raster images preferably represent monuments, landscapes, animals, plants or portraits. In particular, raster images can only represent parts of monuments, landscapes, animals, plants or portraits.

As a variant, a raster image may in particular represent any geometric shape forming a background or part of a background of another image, for example a monument, landscape, animal, plant or portrait. According to this variant, a raster image can cause another image to be emphasized.

The pixels of a raster image are indistinguishable from each other, especially when the raster image is viewed with the naked eye in transmitted light. They can be distinguished from each other in particular when the raster image is viewed under magnification in transmitted light, for example at least 10x magnification, preferably at least 20x magnification. Thus, they form a level-2 security feature.

According to one variant, the pixels of the raster image can be distinguished from each other when observed with the naked eye in transmitted light, thus forming a level-1 security feature.

pixels

"Pixels" means individual elements in a watermark's pattern, similar to pixels in a digital image.

The pixels may have any shape, but are preferably in the form of dots, especially dots having a circular, elliptical or polygonal shape, or in the form of lines, or characters, alphanumeric characters, It can take the form of an ideogram or symbol. A raster image may include pixels of various shapes.

Pixels form the raster elements of a raster image.

A raster image may include pixels arranged at a raster angle, that is, arranged in rows making an angle to the horizontal.

The thickness of the raster elements may be comprised between 200 and 1500 μm.

In the case of pixels having the form of lines, the width of the raster elements, i.e. the lines, may be greater than 50 μm, in particular greater than 70 μm, preferably greater than 100 μm.

In the case of pixels having the form of dots, letters, alphanumeric characters or ideograms, the maximum dimension of the raster elements, ie the pixels, excluding the thickness, may be greater than 50 μm, in particular greater than 70 μm, preferably greater than 100 μm.

A raster image can be amplitude modulated, i.e. the pixels are uniformly distributed and the pixels vary in size, or they can be frequency modulated, or even frequency and amplitude modulated. In particular, from some pixel size, a raster image can be amplitude modulated, and below that pixel size it can be frequency modulated.

A raster can be stochastic, eg have a fixed pixel size with a statistical frequency varying to reproduce various gray scale levels. The pixels may have the same geometry depending on the amplitude or, as a variant, the geometry of the pixels may vary depending on the amplitude.

Placement of the pixels within the image is preferably automatically generated by a software package.

mask

The mask may be made of any suitable material, particularly metal and/or plastic.

The mask contains thin linking elements.

These connecting elements, because of their thickness, leave no or very little visible traces in the watermark, connecting the elements to form the visual pattern of the watermark and correcting the strength of the elements. The connecting elements preferably have a thickness comprised between 20 and 200 μm, more preferably between 30 and 100 μm. The thickness of the connecting elements is preferably constant.

The connecting elements preferably have a width comprised between 20 and 200 μm, more preferably between 30 and 100 μm. The width of the connecting elements is preferably constant.

The connecting elements preferably have a width and thickness comprised between 20 and 200 μm, more preferably between 30 and 100 μm. The width and thickness of the connecting elements are preferably constant.

The connecting elements are preferably elongated elements.

The connecting elements are preferably arranged in a grid. In this case, the minimum dimension (ℓ) of the cells of the grid may be greater than 300 μm, particularly between 300 μm and 5 mm, and preferably between 500 μm and 3 mm.

The connecting elements can in particular be arranged between the base and the top of the elements for forming the light zones they connect. They are preferably arranged between the bases or between the tops of the elements to form the light zones they connect.

The height of the elements to form the bright areas may be constant throughout the mask. As a variant, the height of the elements for forming the bright areas is variable throughout the mask, in order to effect the formation of the watermark to obtain pixels that are somewhat darker in the transmitted light.

The elements for forming the bright zones are preferably made of the same material as the connecting elements. In particular, the elements for forming the bright zones and the connecting elements preferably form an integral part, which provides a more robust mask.

The mask comprises, in at least one area, elements for forming bright areas arranged as pixels of a raster image, and at least one area for forming another type of watermark, in particular It may include areas that do not have elements to form bright areas arranged as pixels of a raster image. Accordingly, there is at least one full raster watermark and at least one conventional multitone watermark obtained by relief, such as an embossment or electrotype watermark. Due to the superposition and/or juxtaposition of the watermarks of , it is possible to obtain a watermark that is hybrid at some point. These "hybrid" watermarks are particularly attractive from a visual point of view. Thus, the raster image of the watermark according to the present invention can only form one part of the pattern, while the other parts, in particular complementary parts, can be other types of watermarks, especially multitone watermarks obtained by embossing. This is particularly advantageous when the watermark forms an image and preferably a monument, landscape, animal, plant or portrait, since, according to a first variant, the watermark according to the invention only forms part of said image. and the other part, in particular the complementary part, is formed with a different type of watermark, in particular a multi-tone watermark obtained by embossing, and according to a second variant, in particular a multi-tone watermark obtained by embossing, the image This is because other parts, in particular the background or part of the background of the image, are formed by the watermark according to the present invention. The part formed by the watermark according to the present invention is highlighted, or used to highlight a part or all of another part of the watermark.

The mask may include a plurality of elements for forming bright regions each appearing as an isolated pixel in the image, preferably, within at least one region of the mask, forming bright regions. The density of elements for this is between 30 and 60 elements/cm 2 , creating many isolated pixels in the resulting image, for example.

The mask may include elements to form clear areas arranged as pixels of a raster image in one area, and apertures to form areas that appear darker than bright areas in another area, which Apertures are also placed as pixels of the raster image. The two regions correspond to the dark and bright regions of the image, respectively. In between, the watermark may include areas where the pixels corresponding to the bright areas are connected within the image and are no longer isolated. The darker areas can have the same opacity as the vellum zone and can even be treated as small zones of the vellum.

At least one of the elements for forming the bright zones may have a maximum dimension of less than or equal to 0.3 mm, in particular comprised between 0.1 and 0.3 mm.

This level of detail is particularly advantageous as it makes imitation of the watermark more difficult.

If the elements for forming the bright zones have a minimum dimension, excluding the thickness, for example a width of less than 1 mm, to ensure dewatering during the manufacture of the paper, holes of very small diameter, for example less than 0.3 mm, are created. It is possible.

The elements for forming the bright zones may have a cross-section that undergoes amplitude modulation along a raster row of the image, allowing raster dots or lines of variable size to be reproduced; and/or a height that undergoes amplitude modulation along a raster column of an image, allowing raster dots or lines with variable opacity to be created. In the latter case, it is possible to change the opacity as well as the distribution of the pixels, thereby changing the brightness of the pixels in the transmitted light, which creates new possibilities in terms of the final appearance of the watermark.

A spatial frequency of the elements to form the bright regions may be constant along at least one raster of the image. The spatial frequency of the elements to form the bright regions may vary along at least one raster of the image. In order to obtain the best rendering of the image, it is also possible to combine the amplitude modulation of the cross section of the elements to form the bright zones, the amplitude modulation of their height and/or the modulation of their spatial frequency.

wire

The wire is part of a papermaking machine and serves to form a fibrous web by dewatering a suspension of papermaking fibers.

The wire may be a cylindrical-mold wire or a Fourdrinier machine.

Preferably, the wire is a cylindrical-mold wire.

Advantageously, the wire comprises a housing oriented towards the outside of the fibrous web in suspension, within which the mask is advantageously disposed. This allows the mask to be protected, allows placement of the mask to be facilitated and opacity variation (distribution of dark/light areas) of the watermark to be optimized. The housing may be formed by embossing the wire. As a variant, the mask can be placed not in a recess of the wire but on the surface of the wire, or it can be placed on the embossed portion of the wire.

The mask may be fixed to the wire by any suitable means, for example welded to the wire, in particular brazed, or even adhesively bonded, pressed or mechanically fixed.

The wire and mask may be fabricated such that the watermark includes at least one raster zone and one non-raster zone. This is, for example, a matter of juxtaposition and/or overlapping of various types of watermarks, eg wires, and the embossing of the mask according to the invention described above.

The watermark may be used in combination with other security measures such as security threads, security fibers or security flakes, which are introduced into the paper during or after manufacture of the paper. More generally, a watermarked paper according to the present invention may include any additional security measures, in addition to the watermark. Among the additional security elements, some can be visually detected in daylight or artificial light without the use of any special equipment. These security elements include, for example, colored flakes or fibers. These security elements are referred to as level-1 security elements.

Other types of additional security elements can only be detected using relatively simple equipment, such as ultraviolet (UV) or infrared (IR) lamps or magnifying glasses. These security elements include, for example, fibres, flakes, particles or microtext. These security elements may or may not be visible to the naked eye and emit light when illuminated, for example by a Wood's ramp emitting at a wavelength of 365 nm. These security elements are referred to as level-2 security elements.

Other types of security elements require more complex detection equipment to be detected. These secure elements may generate a specific signal, for example, when experiencing one or more external exciting sources simultaneously or asynchronously. Automatic detection of the signal, where appropriate, authenticates the authenticity of the document. These security elements contain, for example, active substances, tracers in the form of particles or fibers, which generate specific signals when these tracers undergo optronic, electrical, magnetic or electronic excitation. These security elements are referred to as level-3 security elements.

One or more additional security elements present in the paper according to the present invention or in the secure document according to the present invention may have level 1, 2 and/or 3 security features.

Another subject of the invention is a method for manufacturing a mask according to the invention, wherein the elements for forming the bright zones and optionally the connecting elements are manufactured using an additive method. This allows higher resolution to be obtained than is possible with machining or chemical etching.

"Additive method" means a method in which material is added as opposed to a method in which material is removed, such as machining or chemical etching.

Preferably, the elements for forming the bright zones and, where appropriate, the connecting elements are produced by electrodeposition, which allows a higher resolution than chemical etching to be achieved.

The connecting elements are preferably manufactured using the same additive method as the elements for forming the bright zones, so that they are integral together.

Electrodeposition makes it easy to achieve, if desired, an amplitude change in the height of the elements to form bright zones, such a change being continuous or can be separated

Electrodeposition allows the elements of the mask to be produced with high precision. It is possible to obtain detail at the level of isolated pixels on the order of 0.1mm, and it is also possible to vary the spacing between pixels to create a degrade. A detail value of 0.2 mm is particularly suitable for the resolution allowed by the paper substrate. The largest elements preferably have a size of less than 0.8 mm. Above this value, the elements are preferably manufactured with very small drainage holes, for example holes with a diameter comprised between 0.2 and 1 mm.

The finest details, in transmitted light, can be formed by bright areas within the watermark.

Another subject matter of the present invention is a watermarked paper, in particular obtained by implementing the method defined above, which paper comprises a watermark with bright areas arranged as pixels of a raster image, The bright regions include at least one bright region that appears to the naked eye in transmitted light as isolated pixels in the image. The watermark may include multiple such bright areas.

The watermark may include at least one area in which pixels corresponding to bright areas are no longer isolated but connected. The watermark may include at least one region with isolated pixels that are darker than the bright regions, and these dark pixels are disposed as pixels of the raster image.

The watermark is preferably formed only with bright areas arranged as pixels of a raster image.

The watermark may include an area with clear areas each visible as an isolated pixel in transmitted light, wherein the density of the bright areas in this area is between 30 and 80/cm 2 , and this area is preferably It occupies an area greater than 20 mm 2 within the watermark.

Another subject of the present invention is a method of authenticating watermarked paper according to the present invention, the method comprising examining the watermark in transmitted light to detect the presence of a raster image, the method comprising: Pixels of a raster image appear as bright regions with at least one isolated pixel within the image, and preferably multiple isolated regions within the image, particularly along a raster row of the image. It appears as bright areas with pixels.

The present invention can be used to manufacture any type of secure documents, such as banknotes, passports, and other identification documents or valuable documents.

The invention will be better understood by reading the following detailed description of non-limiting examples of practicing the invention and a review of the accompanying drawings.
1a to 1e show detailed views of a watermark-forming mask according to the present invention;
2a to 2c are cross-sections of examples of masks according to the present invention;
3 shows an example of a mask according to the present invention;
4 shows the resulting image when the mask is viewed in transmitted light;
Figure 5 shows a detail of Figure 4;
5a and 5b respectively show another example of a mask according to the present invention and the resulting image when the mask is viewed in transmitted light;
Figure 6 shows a mask according to the invention placed in the housing of the wire.

3 shows an example of a mask 10 according to the invention. The mask comprises linking elements 15 arranged in a grid, the grid comprising, for example, in the example shown, grid cells of constant cross-section each of a square or rectangular shape. have As a variant, the connecting elements 15 are not arranged in a grid.

1A shows an example of a mask.

The connecting elements 15 connect the isolated elements 18 forming bright areas arranged as pixels of a raster image. The elements 18 for forming these bright zones have a maximum dimension w.

The elements 18 can be placed anywhere with the intersections of the grid formed by the connecting elements 15 .

Figures 1b to 1e show what can be used for the pixels of image elements of non-circular contours.

These may be polygonal elements, for example rectangular elements as shown in Fig. 1b, straight elements as shown in Fig. 1c, or L-shaped elements as shown in Fig. 1d. As shown in Fig. 1e, it is also possible to have elements 18 of different geometries in the same holding grid.

The smallest dimension (L) of the cells is, for example, greater than 300 μm, in particular comprised between 300 μm and 5 mm, preferably comprised between 500 μm and 3 mm.

Referring to FIGS. 2a to 2c , it can be seen that the thickness e _g of the connecting elements 15 is smaller than the thickness e _e of the elements 18 for forming the light zones. The connection elements 15 may form strands crossing at right angles. Some of the strands may be oriented parallel to the rasters of the image, and the spacing between these strands may match the spacing between the rasters of the image.

As shown in FIGS. 2B and 2C , the height e _e of the elements 18 for forming the bright areas may be variable throughout the mask 10 . This allows pixels of higher or lower brightness to be obtained, which increases the number of parameters that can be varied for the purpose of reproducing an image. Varying the height of the elements 18 to form the bright zones makes it possible to form a watermark that is more difficult to reproduce.

In the example shown in Figures 2a to 2c, the elements 18 for forming the bright zones, viewed from above, have a cross-section that varies along the rasters as a function of the size of the raster dots to be reproduced in the image. have

As shown in Figures 2a to 2c, the connecting elements 15 connect the bases of the elements 18 to form light zones. As a variant, the connecting elements 15 connect the upper parts of the elements 18 to form light zones.

The invention is not limited to connecting elements 15 connecting bases or tops of elements 18 to form bright zones. Specifically, the connecting elements 15 can connect the elements 18 to form light zones at points other than the base or top. As a variant, a combination of various concrete cases is required, such as connecting elements 18 via base and/or top and/or other points, for connecting elements 15 to form light zones.

For example, as shown in Figs. 4 and 5, certain elements 18 for forming the bright areas of the mask are isolated, visible as isolated pixels 20, within the acquired watermark 30. and can be seen to be broken bright areas. This is the case at the back of the hair, for example.

The zone 21 surrounding the pixels 20 may have the same thickness as the vellum zone 31 . 6 shows that it is possible for the wire T to accommodate the mask 10 to include the housing 100 .

The mask 10 is disposed within a housing 100, wherein the connecting elements 15 are supported against a flat bottom of the housing ( FIG. 6 ) or at least some of the elements 18 for forming bright zones are It is supported against the flat bottom of the housing 100.

According to one variant, all elements 18 for forming the light zones and/or all connecting elements 15 bear against the flat bottom of the housing 100 . In particular, when the elements 18 for forming the bright zones have a variable height, such a configuration can be achieved, for example, by the housing 100 having a non-flat bottom and/or the relief of the elements for forming the bright zones. It is possible to create by connecting elements along the relief.

The invention is not limited to the examples given.

In particular, one or more watermarks according to the present invention may be placed on paper to interact with other security elements, such as a thread or foil.

Paper can be based on natural and/or synthetic fibers. Preferably, the paper contains natural fibers, such as linen and/or cotton fibers, in particular cotton linters.

Paper can be single-ply or multi-ply. In the multi-ply case, the plies may be colored differently.

Claims (26)

As a method for manufacturing security paper:
creating a watermark using a mask (10) fixed to a wire of a paper machine;
The mask comprises a network of elements (18) for forming light zones in the watermark, said elements being connected by linking elements (15), said light zones are arranged as pixels of a raster image, the connecting elements being invisible in the watermark so that at least some of the elements 18 for forming bright areas are visible to the naked eye in transmitted light. Sufficiently thin to lead to the formation of pixels of a raster image that appear to the naked eye as isolated pixels,
The elements 18 for forming the bright zones are made of the same material as the connecting elements 15, and the elements 18 for forming the bright zones and the connecting elements 15 are integral parts. , wherein the connecting elements (15) are arranged in a grid, and the minimum dimension (l) of the cells of the grid is contained between 500 μm and 3 mm. According to claim 1,
The method of manufacturing security paper, wherein the pixels have a dot shape. According to claim 1,
The method of manufacturing security paper, wherein the pixels have the form of lines or have the form of characters, alphanumeric characters, ideograms or symbols. According to claim 1,
The wire is a wire of a cylindrical mold (cylinder mold), a method of manufacturing security paper. According to claim 1,
The method of claim 1, wherein the wire includes a housing (100), and the mask (10) is disposed within the housing. According to claim 5,
The method of manufacturing security paper, wherein the housing is formed by embossing the wire. According to claim 1,
Wherein the mask is welded or soldered to the wire. According to claim 1,
wherein the wire and the mask are fabricated such that the watermark includes at least one raster zone and one non-raster zone. According to claim 1,
wherein the height (e _e ) of the elements (18) for forming bright zones is constant throughout the mask. According to claim 1,
wherein the height (e _e ) of the elements (18) for forming bright zones is variable throughout the mask. A watermark-forming mask for implementing the method according to any one of claims 1 to 10,
comprising a set of elements (18) for forming light zones;
The elements are connected by linking elements 15 and arranged as pixels of a raster image, the linking elements 15 being sufficiently inconspicuous within the watermark. A watermark-forming mask, wherein the elements for forming thin, bright areas lead to the formation of pixels of a raster image that in transmitted light appear to the naked eye as isolated pixels in the image. . According to claim 11,
The watermark-forming mask, wherein the height of the elements (18) for forming bright areas is constant throughout the mask. According to claim 11,
wherein the height of the elements (18) for forming bright areas is variable throughout the mask. According to claim 11,
Elements 18 for forming bright areas arranged as pixels of a raster image in at least one area, and bright areas arranged as pixels of a raster image A watermark-forming mask comprising at least one other region that does not have elements for forming the watermark. According to claim 11,
A watermark-forming mask comprising a plurality of elements (18) for forming bright regions each visible as an isolated pixel within an image. According to claim 11,
and at least one of said elements (18) for forming bright areas has a maximum dimension (w) of less than or equal to 0.3 mm. According to claim 11,
wherein said elements (18) for forming bright areas have a cross-section that undergoes amplitude modulation along a raster row of an image. According to claim 11,
wherein the elements (18) for forming bright areas have a height (e _e ) that undergoes an amplitude modulation along a raster row of the image. According to claim 11,
wherein the spatial frequency of the elements (18) for forming bright areas is constant along at least one raster of the image. According to claim 11,
wherein the spatial frequency of the elements (18) for forming bright regions is variable along at least one raster of the image. According to claim 11,
wherein the connecting elements (15) have a thickness (e _g ) comprised between 30 and 200 μm. A method of manufacturing the mask according to claim 11,
The elements 18 for forming bright areas leading to the formation of pixels of a raster image that in transmitted light appear to the naked eye as isolated pixels in the image are electrodeposited. A method for manufacturing a mask manufactured using the method. As a watermarked paper obtained by implementing the method according to any one of claims 1 to 10,
A watermark having bright regions arranged as pixels of a raster image, said bright regions being isolated pixels in the image to the naked eye in transmitted light. A watermarked paper comprising at least one bright area visible as . According to claim 23,
wherein the watermark is formed solely of bright areas arranged as pixels of a raster image. According to claim 23,
wherein the watermark comprises a number of bright areas each appearing as an isolated pixel within the image. A method of authenticating the watermarked paper according to claim 23,
inspecting the watermark in transmitted light to detect the presence of a raster image;
wherein the pixels of the raster image appear to the naked eye as bright areas with at least one isolated pixel within the image.

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